I've been trying the electrolysis method on some smaller parts in a plastic garbage can and can say that it works quite well. Takes time but there are not harsh chemicals and very little mess. My kids got a hood he needs to de-rust and I'm trying to talk him into building a tank out of wood and plastic sheeting to give it a shot. The process leaves a black finish that I understand is magnetite, but it comes off with a wire wheel and leaves shiney metal behind. Wonder if you could use a pool and do the whole car? LOL